The invention concerns a detection device for detecting persons or objects and the direction of movement thereof, comprising a sensor arrangement for detecting electromagnetic radiation with the wavelength of visible and/or invisible light, which is reflected or emitted by a person or an object, and an evaluation unit which is connected to the sensor arrangement and adapted to derive a signal from the radiation detected by the radiation sensor arrangement and to deliver a detection signal for as far as possible each object or person detected by the radiation sensor arrangement. In particular the invention concerns a counting device for persons, which is connected to a corresponding detection device.
An area of use of detection devices of that kind is the detection of persons who pass through an entry or exit region of a means of transport in order to count the passengers who pass into or leave the means of transport. DE 42 20 508 and EP 0 515 635 each disclose detection devices which, in relation to the intended direction of movement of the passengers, have sensor elements which are arranged one after the other, and which ascertain the direction of movement of detected persons by correlation of the radiation detected by the sensor elements. Detection devices of that kind are thus capable of ascertaining not only the presence of an object or a person, as in the case of a simple light barrier arrangement, but also the direction of movement of the object or person. A problem here however is that of reliably detecting persons who are not moving with a specific destination in mind but who for example are standing in the entrance region of a bus, or distinguishing the signals which originate from various people who are in great mutual proximity.
One approach to resolving the last-mentioned problem is set forth in DE 197 21 741. It is proposed therein that a continuous spacing signal for detected objects should be formed and the spacing function obtained in that way should be compared to predetermined or stored spacing characteristics of known objects in order in that way to obtain information about the number, movement or nature of the objects. In accordance with DE 197 21 741 that is effected by means of an active signal generator/detector arrangement. Active means that the detector records the radiation which is delivered by the signal generator and reflected by the object or the person.
It is known from DE 197 32 153 for two images of a person, which are recorded from different vantage points, to be associated with each other on the basis of characteristic image features, in order in that way to obtain spatial information.
An object of the present invention is to provide a detection device which in a simple manner permits even more accurate object or person detection or counting.
In accordance with the invention that object is attained by a detection device of the kind set forth in the opening part of this specification, which includes individualising means which are connected to the evaluation unit and which are adapted to produce information individualising an object or a person, and which is connected to a store adapted to store at least a portion of the variation signal and the information individualising the object or the person, as a characteristic parameter, in association with the variation signal. In that respect the parameter can be derived directly from the variation signal or can be derived from the variation signal and an additional signal which can be obtained by an additional passive sensor and/or derived from an active radiation source. The parameter can also be one-dimensional or multi-dimensional, that is to say for example a matrix or a vector with a plurality of values which in particular individualise a person.
The invention is based on the idea of combining in per se known manner a variation signal which is to be produced passively with at least one characteristic parameter so as to afford an at least two-dimensional signal or parameter matrix which combines items of information about the time variation of the radiation detected by the sensor arrangement with additional items of information. Such an arrangement makes it possible to derive a movement signal by signal correlation from the variation signal, in a manner known per se from DE 42 20 508 or EP 0 515 635, and to associate that movement signal with an individual object or an individual person as reliably as possible by means of the characteristic parameter or parameters. Preferably the characteristic parameter describes a person-individual parameter such as hair color, height, stature, etc.
The additional characteristic parameter can admittedly be determined solely from the signal morphology in the case of a passive arrangement. However a further preferred underlying notion of the invention is for the detection device to be provided with additional means for determining the characteristic parameter. Among the large number of additional means which can be envisaged, two alternatives have proven themselves to be particularly appropriate, in an unforeseeable fashion, namely a radiation source for implementing an active arrangement of the detection device, or alternatively or additionally an additional sensor for detecting a further signal besides radiation, for example an acoustic signal or a scent signal.
In the case of an active arrangement with a radiation source the additional parameter can be ascertained by evaluation of the radiation reflected by an object or a person, in relation to the radiation emitted by the radiation source. In that way, it is possible to obtain information about the transit time of a signal from the radiation source by way of a reflecting person to the sensor arrangement or the degree of reflection.
The preferred frequency or wavelength range of the electromagnetic radiation, for the detection of which the sensor arrangement is adapted, is the range of greater than 1400 nm. In the case of an active arrangement with a radiation source, that wavelength range also applies in regard to the radiation source. It has been found that, in that wavelength range, it is possible to achieve both an advantageous signal-noise ratio and also a high degree of sight safety. In particular a radiation output in that wavelength range can be more than 1000 times greater than for example in the region of 1050 nm, without that involving any danger to health.
In principle, preferred embodiments of the detection device are those which are adapted to be arranged in entrance and exit openings such as for example doors of vehicles or rooms.
A preferred area of use of the detection device is counting passengers for example in buses. In particular for that area of use, the detection device is preferably connected to a locating device such as for example a GPS receiver. In that way the numbers of passengers ascertained by the detection device by means of a counting unit for the entering and exiting passengers can be associated with given route sections or stops of a bus. Together with an optional evaluation unit, integrated vehicle management is thus possible. That can be used for an entire vehicle park if the detection devices and locating devices of different vehicles are adapted to be connected to a central station by way of radio.
In a preferred arrangement, the radiation source is arranged for example in the entrance region of a vehicle, in such a way that the radiation from the radiation source impinges from above on the person passing through the entrance region and is reflected from the top of the head of the person in such a way that the height of a person can be determined from the transit time of the signal. The characteristic parameter to be stored then corresponds to the height of the person. The variation signal which is recorded synchronously can be specifically associated with a person of the corresponding height, by means of the characteristic parameter. As most people differ in height at least within certain limits, it is possible in that way to provide for a substantially person-individual association of variation signals, so that even those variation signals which result from the radiation from two people who are at a great proximity from each other are to be associated as coming from two different people.
An essential difference in relation to the device disclosed in DE 197 21 741 is that for example in the case of the operation of determining the height of a person, for forming the characteristic parameter, it is not the spacing functionxe2x80x94that is to say the variation in spacingxe2x80x94that is stored and compared to other spacing functions, but only the minimum of the spacing between the radiation source and the sensor arrangement on the one hand and the top of the head of a person on the other hand.
Fundamentally, both the systems known from DE 42 20 508 and EP 0 515 635 and also that known from DE 197 21 741 are based solely on the correlation of two signal variations or functions. In the case of the system proposed herein the characteristic parameter is not derived from a comparison or a correlation of functions among signal variations, but from one signal alone. That signal can originate for example from an infrasound sensor for detection of heart sounds and thus the heart rate, or from the arrangement, already described above, for detection of the height of a person, or also a sensor matrix arrangement on to which is projected an image of the persons passing through the entrance region, so that a parameter which characterises the contour of the persons can be obtained from the image.
The sensor matrix arrangement can be connected to a radiation source of the above-described kind to constitute an active sensor so that it is possible to record a three-dimensional height contour of a detected person as a characteristic parameter.
Preferably at least one suitable sensor is provided in each case for recording such or other person-individualising signals. That sensor is preferably switched on when the variation signal shows that the detected person is just at the greatest proximity in relation to the sensor. Alternatively the sensor remains continuously switched on and only that portion of the signal originating from the sensor, which was recorded at the time of greatest approach to the sensor, is evaluated. For that purpose the detection device preferably includes suitable locating or distance-determining means and a selection unit which is connected thereto and which selects the appropriate signal portion originating from the sensor, for further processing.
In subtly differentiated or sophisticated configurations of the invention a plurality of characteristic parameters or parameter variations can be simultaneously obtained and combined together in order to permit still more accurate differentiation of the items of information obtained and thus still more specific individualisation of the detected persons.
Further preferred embodiments are set forth in the appendant claims.
These include in particular detection devices with an additional sensor for person-individual features such as height, build, hair color, heart sounds or scent of a person or an object.
The invention will now be described in greater detail by means of an embodiment.